It is sung in church on the night of 24 December annually at matins in Majorca.
The Song of the Sibyl (Catalan: El Cant de la Sibilla) is a liturgical drama that has been performed on Christmas Eve in churches in the Balearic Islands, Spain, and Alghero, Sicily, Italy. This song was originally sung in a Gregorian melody. The music that accompanied it in Majorca, with exception of a few variations, was the same as that heard in other locations across the Iberian Peninsula. In the past, the song was sung by a Presbyter but later it was replaced by a boy. Although the song was meant for a Sibyl woman (prophetess), for many centuries women weren't allowed to sing in church.
The performance begins with a boy or girl accompanied by two or more altar boys or girls, the chant marks the annual Christmas Vigil. In the chant, both singers hold swords in front of their faces as they stroll towards the chancel, while the altar boys or girls carry candles. The sword is used to draw a cross in the air at the end of the song.
There are only a few variations among the versions of the chant sung on the island: they are all sung a cappella with music interspersed between each verse provided by an organ. Often the singers wear white or colored tunics with embroidery around the neck and hem, and a cape over the top. The head is covered with a cap that matches the tunic.
On Majorca, all the parishes take part in this rite, with old and young generations working side by side as singers, costume-makers, celebrants, and other helpers to keep it alive. The oral transmission of this song resulted in the creation of different variations and models, just as it did with the text. Early Musicologists and Folklorists in the 19th century became intrigued by this chant, which led to them transcribing the different known versions of the song. The versions played today follow these transcriptions as models.
Following the Council of Trent (held in 25 sessions from 1545 to 1563), the Song of the Sibyl was almost totally abandoned throughout Europe. Nevertheless, it was performed on Mallorca as early as 1575. Since then, today's performer increasing numbers of cities in the Catalan-speaking world are reviving the tradition. In most churches where the song is sung today, it is sung by both a boy and a girl, although some places may have a little girl or woman sing it.
References
(https://ich.unesco.org/en/lists?text=&inscription[]=00004&multinational=3&display1=inscriptionID#tabs) (https://en.wikipedia.org/wiki/The_Song_of_the_Sibyl) (https://en.wikipedia.org/wiki/Khachkar)